Cause-effect dynamics of computer and network systems for QoS

To provide Quality of Service (QoS) demanded by many online services (e.g., e-commerce), computer and network systems need to have QoS monitoring and adaptation which must be based on cause-effect dynamics relations among service activities, the state of system resources, and the QoS performance of service processes. This paper presents our study on cause-effect dynamics models for one of computer and network services, the voice communication service with the throughput of network data as the QoS feature of interest. Experiments are conducted to obtain computer and network data under various service conditions that are set up using three service parameters: The sampling rate, the number of clients and the buffer size. The experimental data is then analyzed. We uncover four major types of cause-effect dynamics. We found a set of five system state variables concerning the memory, CPU, process and IP resources that are significantly affected by the service parameters and are closely linked to the network throughput performance of the voice communication service. New insights are also gained about satisfying high QoS demands by properly increasing the size of the buffer which holds the network data before the data transmission.